Of members constructing the rolling bearing, a retainer and a sealing member are often constructed as a molding of a synthetic resin composition or a polymeric elastic body. Engineering plastics and synthetic rubber derived from fossil resources have been adopted for the synthetic resin composition and the polymeric elastic body.
For fear that biological environment is harmed when a used rolling bearing is disposed of as industrial waste, a retainer made of synthetic resin having biodegradability, a sealing member made of resin, and grease-applied rolling bearing are proposed (patent documents 1 and 2).
But even though the synthetic resin composition having biodegradability is used, the polymeric matrix is eventually a source of carbon dioxide emissions owing to biodegradation or combustion when the polymeric matrix composing the synthetic resin composition is plastic or the like derived from the fossil resource. Thus the polymeric matrix has a problem that it gives an adverse effect on global warming
Because the bearing in which the molding of the synthetic resin composition is used as the retainer and the sealing member has a high degree of design and a high productivity and contributes to a decrease in the weight of the bearing, there is a growing demand for expanding areas of use of such a bearing in recent years. But the bearing having its members made of the synthetic resin has a problem that the synthetic resin gradually deteriorates because of use at a high temperature for a long time unlike a bearing totally made of metal, which makes it impossible to make the continuous use temperature high and the endurance time long.
The molding made of the synthetic resin composition containing a raw material derived from the biomass has a problem described below, although the raw material derived from the biomass is capable of decreasing the amount of carbon dioxide generated from a time when the molding of the synthetic resin composition is produced until it is discarded and contributing to restraint and prevention of an increase in the concentration of the carbon dioxide in the atmosphere or a decrease of the concentration thereof: Because the polymer has amide bonds and ester bonds inside it, the polymer becomes low-molecular owing to hydrolysis of the amide bonds and the ester bonds caused by an atmosphere gas and thus the mechanical strength thereof gradually deteriorates. Therefore there is a demand for the development of a measure for preventing the deterioration of a polymeric material for the bearing.    Patent document 1: U.S. Pat. No. 3,993,377    Patent document 2: Japanese Patent Application Laid-Open No. 2004-68913